Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

931
FXUS63 KLOT 262359
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
659 PM CDT Fri Jun 26 2026

.KEY MESSAGES...

- A few thunderstorms are possible Saturday night into Sunday
  morning, mainly west of the Fox Valley.

- Dangerous heat will build across the area next week, with
  afternoon heat index values over 100 degrees each day
  beginning Monday.

&&

.DISCUSSION...
Issued at 205 PM CDT Fri Jun 26 2026

Ongoing showers will continue through the evening and
overnight. Most of the rain thus far has been fairly minimal.
Light rain can be expected as far north as Interstate 90, but
the better coverage will remain closer to the higher moisture
plume south of Interstate 80 with localized heavier downpours
possible along and south of US 24. The better instability
remains well to the south and out west near the area of surface
low pressure. Thus, pulled the chances for thunder for the rest
of today for much of the area, with any lingering (less than 24
percent) chance around US 24.

The surface low, currently in western Missouri, will slowly
move northeast and pass just south of the forecast area
overnight. The models slowing the progression of the low gave
confidence in maintaining chance PoPs for areas southeast of
I-57 Saturday morning, though overall drier conditions are
expected tomorrow. Winds will remain out of the northeast
through the day on Saturday. High temperatures are expected in
the 70s to low 80s inland with cooler upper 60s to low 70s along
the lakeshore.

While Saturday is looking to shape up as a nice day locally,
the overall atmospheric pattern will be changing tomorrow. An
upper level low out over the Rocky Mountains will continue to
deepen and sink farther south over the western CONUS.
Subsequently, an upper level ridge will amplify northward from
the Gulf and deepen. This amplified pattern will set up broad
southwest flow over the Plains and Mississippi River Valley. A
weak wave is expected to eject out of the upper level low and
move toward Wisconsin. Decent mid-level lapse rates could
support thunder and the presence of a slug of moisture with
warm air advection and isentropic upglide could support showers
and a few thunderstorms in the overnight hours. However, this
will be moving in toward a drier and less favorable air mass,
and models are already responding giving confidence to lower
PoPs. Perhaps a few showers fester into Sunday morning, but
generally drier (and more humid conditions) are expected during
the day.

More concerning, starting on Sunday, is the potential for
dangerous heat next week. A strong upper level ridge will sit
east of the Mississippi River through the week. Southwest flow
will continue to advect in warmer air as 850 mb temps increase
over the area from 15 to 20C on Sunday to around 25C on Tuesday
(the current expected highest temperature forecast of the
stretch). Temperatures are expected to climb into the 90s for
most of the forecast area, and with overnight lows only in the
mid to upper 70s, little relief can be expected at night.
Additionally, the southwest winds will bring the afternoon
temperatures all the way to the traditionally cooler lakeshore.
Dew points climbing into the 70s will make for humid conditions
and drive heat index values up to around 105 F.

Setting a record high temperatures is not a guarantee
(especially for any records that are 100+, like much of KRFD),
but a Climate section has been created below for interested
individuals. Two big questions for this heat event will focus
on the center of the upper level high embedded in the ridge: 1.)
where will its location be? And 2.) how strong will it remain?
Monday and Tuesday look to be a good chance for these hot
temperatures to set up, but there is greater uncertainty for
mid-week and after. If the high were to weaken or even set up
along and south of the Ohio River Valley, there could be a
convective complex that could ride over the top of the ridge and
bring not just showers and storm chances to the area, but also
some relief from the temperatures. So no changes were made to
the splotchy chance PoPs that the NBM provided for the middle
and end of the week. However, recent models have trended towards
a slightly stronger high. If that were to materialize, the
region could be set up for not just drier conditions, but an
extended period of heat indices over 100F. It`s still far too
early for any headline (e.g. Watch, Warning, Advisory), but
there is growing confidence in the first heat wave of the year
leading into the holiday weekend.

DK

&&

.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 659 PM CDT Fri Jun 26 2026

While remaining mainly non-impactful, light showers/sprinkles
continue to redevelop along the I-88 corridor early this
evening. Have pushed the end time of the VCSH mention at the
Chicago area terminals to 3Z to account for this. The overall
trend should still be toward decreasing coverage over the next
few hours. Hi-res guidance does hint at the potential for spotty
light showers or sprinkles lingering across portions of the
area overnight into the day on Saturday, though this is more
likely to remain virga and have accordingly left the TAFs dry.

While VFR conditions are currently forecast through the period
we will be monitoring a couple areas of LIFR to IFR stratus
hugging the lakeshore that may attempt to ooze inland later this
evening. The current expectation is that it will struggle to
hold together with inland extent and will handle any updates
tactically based on observational trends. Any MVFR stratus
associated with the system drifting across central IL/IN could
also briefly reach the terminals during the day on Saturday
though the general trend has been toward it remaining mainly
south of I-80.

Winds will remain northeast to east through the period around
5-10 kt.

Petr

&&

.CLIMATE...
Issued at 143 PM CDT Fri Jun 26 2026

     ....Daily Record High Temperatures........

            Chicago (KORD)      Rockford (KRFD)
June 28      101F (1951)          103F (1934)
June 29       97F (1954)          103F (1931)
June 30       99F (1913)          102F (1954)
July 1       103F (1956)          101F (1931)
July 2        99F (1970)           99F (1910)

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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